Wallboard



Marh 21, 1944. p, W CQDWISE 2,344,600

WALLBOARD Filed March 6, 1941 INVENTOR iff/0D M Comu/5E @wim ATTORNEY manna sind cualitiesintiieiinislied'liever.

l Patented Mar. 21, i944 UNITED STA-'ras PATENT OFFICE 2,8443 i l 'Philip w. assigner ai mw Application Mmh 6, 1941, Serial N0.

6 Claims.

This invention relates to iibrous sheets and more especially to iibrous sheets ma'de of plies in a paper-making process. The invention particularly relates to cover papers for wallboards of the type which have a core of hydraulic. setting material in set condition to the face of which core the cover sheets are bonded. Gypsum wallboards andiathareofthistype.A n

In themanufacture of wallboards of the type above referred to, and particularly in gypsum wallboards. the core' material is fed between two cover papers which are continuously delivered 'to beaters so that it is carried throughout the papermaking process and is uniformly distributed in` the whole of the felted structure of the paper or the board making machine. In many cases the margins of at least one of the cover papers are folded over the edge portions of the plastic mass of the gypsum mortar or slurry and the coverpapers are pressed'upon the core material before it is set to form the board with the 'desired thickvness'and width.4 In part because of the fibrous nature of the cover sheets and in part because of the inclusion, usually inthe core material, oi'y -an adhesive, the cover papers become bonded to the core material. These cover papers not `only 4provide a finish for the. wallboard when one or both of them are made with a finish or decorative surface, but. they also cooperate with the core as tension members to provide the desired/strength in the board. It is important', therefore. that these cover papers shall be preserved undamaged. Care is exercised in handling 0f the materials in manu- Vfactureandtheboardswithnishedsuri'acesiiire bundled with the iinished facs together or otherin a particular ply thereof if the paper as it is made upon the paper machine is produced by felting together separate webs or plies. In other cases the sizing is incorporated in the particular ply in which itis desired `to have it' present by introducing the sizing at the 'headbo'x onthe Apaper machine or at some iother point which will incorporate the sizinsin the particular ply but avoid its incorporation in the. other plieswhich go. tc make up a plied paper. In still other cases.

the sizing may be applied as a surface application to the ilnished paper at the calender stack. or afterfthe paper is dried andnished.

In cover papers commonly used-inthe manu--l facture of gypsum wallboard some of the plies, other than those which' lie immediately adjacentl or in contact with the gypsum mortar or slurry which is to form the core, have incorporated in them a sizing, for example, a rosin sizing. In

l practice the' cover sheet may be made with a plurality of plies, for example, seven.` The twopiies which -are-at the face of the sheet opposite that which is to lie in lcontactwith the core materialy wise covered toprevent injury to the coverpapers in shipmentand storage.

It has been found, however, in some climates, particularly in the tropics, that some insects, such as termitesand those known as comejenes, will attack the paper either because of its fibre content or because of the other inzredi'e'ntsrsuch as' sizing or'othe; organic material, which are usedin the manufacture ofthepaper.

It is an object of the invention, therefore. to produce 'wallboarisl of the type above described which will not be subiect-to such attack and if 4attacked will have a toxic elect upon the insects and thus prevent their-migration throuahoutthe -coverpaperstmcturewith consequentdestruction' of the and decorative value of the 'Ith'ss'hesn the practice in tbemanufacture of many -kindsfof papers to incorporate sizing materialsmthe'xormqrstsrcnvsiueaorsodafuins.

at various'plsces in the paper-L' -prosior the of murine deminum sulphate. The

of the gypsum lboard constitute the lace. liner. There may be incorporated in the f'elted struciaire o1' these plies a rosin sizing set with alubetween the unsized plies'and the face liner plies areknownastheiillerand mayalsobesiznedwithV rosin sizing set with aluminum sulphate. 4These -fillerl plies, however. are of cheaper stock than 'rhs purpose of providing the combinacion of sind and unsiled plies. described. is to mord intheiinishedcover'sheetresistancetotheabsorption o! waterin the iinishedface of the boardwhileatthe'sametimeinsuring-acondi- 'tion'for the pli which a'rein contact 4 withtlie corematerislwhichwillassureagoodbcndthereplies. usuallytwo, which lie adiacentor in contact with the core material j are formed without sizinz. The three lilies lying and may assist in carrying the adhesive which is incorporated in the core material to the interface between core and cover papers and also to aid the migration of particles of the calcined gypsum to cause their interlocking with the libres of the unsized plies of the paper upon setting.

VIn the treatment of cover papers, according to the present invention, it is important that -these characteristics of the cover paper and the functions referred to, should not be interfered with or eliminated. Moreover, in the manufacture of gypsum board and similar materials lwith hydraulic setting core materials, for the most part the water contained in the mortar or slurry of the core must pass out through the cover papers upon drying. Thus the cover papers must not be impregnated or sealed to such an extent that moisture, particularly as vapor, cannot travel through them and be evaporated and eliminated at the outermost face of the face liner. Nevertheless, the sizing contained in' the plies described will resist rapid migration of liquid water. Thus the migration of soluble solids contained in the water into and through these plies and upon the outer face of the board will be largely prevented. On the other hand, the absorbent plies which are in contact with the core material are in such a condition as to readily absorb water containing soluble solids, which vsolids upon evaporation of the water will be deposited in the felted structure of said absorbent unsized plies. Sonie passage of water and the Y solid soluble content thereof may take place into so that t some'ext'ent the solids contained in the water may be deposited in such sized plies.

The drawing illustrates to enlarged scale a section of a wallboard having a core of hydraulic setting material I, as of calcined gypsum, 'with cover papers-3 at both faces thereof. Each cover paper 3 is composed of seven plies, the outer two plies 5 of which may be of sized stock providing a finished surface for the wallboard. The three plies 'l lying at the center of the cover paper 3 commonly known as the ller or, centers, as above stated, if desired, also may be sized but need not be of as high quality as the liner plies.

vThe two plies 9 whichlie next to the core l are those which in the particular embodiment being described especially concern the invention. These plies do not carry the rosin sizing but are left absorbent for the reasonsabove set forth.

These plies 9, however, are treated with a toxic impregnating material in the manner described.

It will be understoodthat the invention is' not limited to the illustrated embodiment, Variations may be made in the number of plies utilized for the cover papers and also in the number In order to prevent the destruction of the cover V l all the ilbrcs thereof and the structure substanq tially from onevface to the other carry the toxic material. Such insulating boards are not of the type of, -nor do they function as do the cover papers used in wallboards having a core of hydraulic setting material with which the cover papers cooperate for strength and finish in the manner above described.

In the cover papers, which are the subject Aoi! the invention, the conditions are such thatthe treated cover paper carries the toxic mate- Qrials so that they ,do not. appear upon the exposed face of the board or adjacent to this exposed surface. Theydo, however, lie in those v portions of the cover paper beneath the surface, and particularly in the absorbent unsized plies adjacent to. the coreso that the insects, which have the habit of boring and devouring the inner or :hidden portions of the nbre structure material,F will encounter the toxic material and be subject' to its toxic effect. Net only 'is it desirable to prevent the appearance upon the face of the board of the solids which may migrate tothe surface of thescover paper and thus spoil 'theflnish thereof, but it is also desirable or essential that such toxic materials shall not be carried upon the face of lthe board because of the irritating physiological effect of any substantial amount thereof.

of plies which are sized with rosin or other sizing material. Variation also may be made in the number of plies which arev treated with the toxic material.

The invention utilizes as a toxic material one which does not interfere with the adhesion of the cover papers to the core material or elimination of the water therefrom or with other mechanical and physical characteristic requisite for such products having a hydraulic setting core between coverl papers. This toxic material is preferably water soluble so that it may be absorbed by the unsized absorbent structure of the cover paper and may to some extent migrate toward and into the inner sized plies. It, moreover, is of such character as not to destroy either the bres or the ilbrousstructures or the sizings carried thereby. To simplify the operations, the toxic material may be applied to the unsized side of the cover paper as the paper sheet is calendered at the calender stack of the paper making machine.

Tonic materials of the class designated as soluble chlorinated phenol derivatives may be used for the purposes of the invention. A particular example of such a material is sodium4 vpentachlorphenate. By suitable devices thistoxic material in solution, particularly in solution in water, is applied to that face of the sheet which will become bonded to the core material. In the preferred method of application of the toxic material to the covr sheet a 10% solution of the toxic material, for example, in the form of sodium pentachlorphenate, may be prepared by dissolving 25 lbs. of the sodium pentachlorphenate' in 250 lbs. of warm water at a temperature of '100 to 150 F. Thesolution may be placed in a container and run therefrom into a water box incontact with one of the rolls of the rst'stack of the calender. In this way the solution maintained, at say,'l00 to 150 F. may be delivered into the nip of the rolls of said stack in contact with that face of the cover sheet which is unsized and will lie in contact with the core material.

Because of the absorbent nature of this ply. an

- and 28 lbs. per ton of the cover paper with which it is incorporated. This represents between .9%

and 1.4% of the dry solid sodium pentachlor,

phenate based on the weight of the' finished dry In the ordinary practice of sizing of the sized paper. This amount of toxic material is suilicient to render the paper distasteful and toxic to the insects.

In the manner above described some migration of the toxic material into the sized plies `may take place during the drying operation and while the wallboard ages. Because of the construction of the cover paper and the amount of toxic material and the concentration thereof as applied to the unsized sheet of the board, however, rapid migration 4or a high degree thereof into'- and through the'sized plies is prevented so that con centration of any substantial amount of the toxic material upon the face of the board is prevented. The toxic material selected for the purposes the `function of the unsized ply which is at that face of the paper which will contact the core material. The absorption of water by this ply and the migration of adhesive and gypsum particles or whatever resulting action takes place to secure the bond are maintained. The toxic material is of the invention is such as will not interfere with of such character and is applied to the paper in such proportions that it does not iill up the structure of the ply at the core contacting face of the cover paper nor does it interfere with the usual characteristics of the cover paper as determined by tests for strength, flexibility, adhesive capacity, splitting of the plies one from the other and other tests to which the cover papers are usually subjected.

While the invention Ahas been described above in connection with the application of the toxic materialat the calender stack the toxic material suitable for the purpose and-particularly a chlo` 1 i in both outer plies of paper for gypsum lath.

Other toxic materials :may be used for the purpose of the invention` which will preserve the characteristics of the cover paper for its bond to the core material and will not interfere with migration of the water from the coreas ded scribed above. For example, a dilute solution oi.

mercurio chloride or sodium arsenate may be.

used, although for ordinary purposes they are .not desirable because oftheir extremely poisonous nature. Inorganic salts, such`as copper sulphate, zinc chloride or barium chloride may also be used although their toxic eiect is not so great as that ofl a soluble chlorinated phenol def` rivative, which may be in the form of the pentachlorphenates of the alkaline metals. Because of its cheapnessand availability sodium pentachlorphenate is preferred. i

plies with rosin it is customary to use alum, aluminum sulphate, to precipitate the rosin from an alkaline suspension in water. Normally an excess of alum is necessary and the excess remains in the sized plies. Migration of the vtoxic material to the inner sized plies and, as well, absorption of the alum by the unsized plies as the web is formed brings the toxic material in contact with the alum. 'The sodium pentachlorphenate, normally of alkaline character or requiring alkalinity for its solution in water, is converted by reaction with the acid alum to the insoluble pntachlorphenol which therefore becomes permanently fixed in the paper.

Having thus described my'inventicn, I new claim:

1. A wallboard comprising a core oi.' hydraulic setting material in set condition between cover sheets of felted fibrous material, and a toxic sub stance' carried by said fibrous sheets at the portions thereof removed from that face ofthe sheet which is exposed in the board.

2. `Awallboard comprising a core of hydraulic setting material in set condition between cover sheets of telted brous material, said cover sheets consisting oi' a plurality of plies of felted iibres, one of said plies carrying a sizing material resisting passage of liquid through said ply by capillary action, and a toxic substance.carried by a ply of said fibrous sheets which lies between said sized ply and said core.

3. A wallboard comprising a core of calcined gypsum in set condition, and a cover paper bonded to said calcined gypsum core said cover paper comprising a plurality of plies of felted iibres 'felted together to form said cover paper, and a toxic substance carried by at least the ply of saidV cover paper which is in contact with said core.

4. A lwall-board comprising a-core of calcined gypsum in set condition, and a cover paper bonded tosaid calcined gypsum core, said cover paper comprising a plurality of plies of felted libres felted together to form said cover paper, the outermost of said plies bein-gfof such compositio`n and finish as to provide on said wallboard a finished face, and a toxic substance carried by at least the ply of said cover paper which is in contact with said core but not extending in said cover paper to the finished face of said outermost ply.

5. A wallboard according to claim 1 in which said toxic substance is sodium pentachlorphenate. 6. A wallboard comprising a core of hydraulic setting material in v'set condition Ibetween cover sheets of felted fibrous material, said cover sheets consisting of a plurality qf plies of felted fibres.

`one of said plies removed from said core having incoffporated therein a sizing material resisting the passage of liquid through said ply by capillary action, the ply in contact with ,said core being unm sized and having a toxic substance incorporated therein.

PHILIP w. coDWrsE. l 

